Electrode spacer



Jan. 18, 1949. J. A. M. VAN LIEMP ET AL 2,459,476

ELECTRODE SPACER Filed April 26, 1946 Patented Jan. 18, 1949 ELECTRODESPACER Johannes Antonius Maria van Liempt, Frits Prakke, HendricusJohannes Landsbergen, and

Jules Henri Marie van Uden,

Eindhoven,

Netherlands, assignors, by mesne assignments, to Hartford National Bankand Trust Company, Hartford, Conn., as trustee Application April 26,1946,` Serial No. 665,012 In Germany June 1.6, 1942 Section l, PublicLaw 690, August 8, 1946 Patent expires June 16, 1962 6 Claims. 1

This invention relates to an electric discharge tube comprising anelectrode system in which the electrodes are maintained at the correctrelative spacing by means of plateor disc-shaped members. The inventionalso relates to members of this kind and to a method of manufacturingthem.

` For supporting electrodes and other metal components or dischargetubes and maintaining them at the correct relative spacing, generallyfor centering them, it is common to use a small mica plate which for.example by stamping has formed in it a plurality of apertures throughwhich the supporting members of the electrodes extend. Generally, such aplate is arranged at each end of the electrode system.

Although satisfactory centering of the electrodes is thus ensured, thisconstruction has the disadvantage that at the areas at which the saidplates are arranged there is insumcient electric screening between thevarious electrodes. In order to obviate this disadvantage it has beensuggested before to provide `supplementary Screening means, for examplein the form of small metal plates or metal layers arranged in close nproximity to or on the mica. This construction, however, also entailsdisadvantages; thus, for example, supplementary members have to besecured in place and the construction of such tubes is thus renderedmore involved; in addition the screening thereby provided is not quitesatisfactory since these conducting members cannot be continuedthroughout the surface of the mica plates but,` in order to avoidshort-circuit, must end at a certain distance from the positioningmembers of the electrodes. Lastly, there has been the disadvantage thatwhen driving occluded gases from the tube components by high-frequencycurrents during exhaust the metal plates or layers that assume a hightemperature heat the mica to such a temperature that the mica loses itsmechanical rigidity. i

The invention provides a simple construction which ensures satisfactorycentering `and satsfactory screening at one time. For this purpose, theelectrodes of an electric discharge tube according to the invention aremaintained at the correct relative spacing by metal plates or discswhich have formed in them apertures for centering the electrodes andother conducting component members and which are supercially coated withan insulating layer.

The use of centering members thus constructed ensures that satisfactorycentering and satisfactory screening are simultaneously secured in a(Cl. Z50-#275) simple manner. Centering is effected in the same mannerwith mica plates in that the stay or positioning members of theelectrodes or these electrodes themselves are passed through aperturesand thus, due to the fact that the plate is coated superiicially,including the aperture walls, with an insulating layer, satisfactoryinsulation between the electrodes is obtained. On the other hand, thescreening is also very complete due to the fact that the plates areconductive inside and only contain a very thin insulating layer on theoutside. Such screening `could not be achieved by means of the knownconstructions. The conductive part of the plate may be connected to agiven potential, for example, by connection to one of the electrodes orcomponent members. further advantage consists in that these spacers mayreadily be formed into a given shape so that they can be used not onlyin the form of a small plate but also as a curved object or provided forexample with projecting tags.

For constituting the spacers here described use may be made of variousmetals or metal combinations; thus, for example, use may be made of asmall metal plate coated with any insulating layer. An example thereofis a tombac plate coated with an insulating enamel layer. In addition,use may be made of a small metal plate `which is superficially oxidizedand is thus provided with an insulating layer; in such cases aluminiumor aluminium alloys may be chosen with advantage to constitute the metalsince it is possible for aluminium to be quite readily coated with adense oxide layer. Lastly, use may be made of small plates made of metalor metal alloy and coated with a further metal which is then oxidized.One example thereof is an iron or a nickel plate which ischromium-plated, the chromium layer being then superficially oxidized.`In respect of the last-mentioned example it must be borne in mind thatif in the opening part of the specification and in the claims referenceis made in Very general terms to a metal or a metal alloy which aresupercially coated with an insulating layer these terms are to beunderstood to include a metal or metal alloy which is rst coated with afurther metal, as is illustrated in` the above-mentioned example.

An insulating oxide layer may be applied by any of the well-knownmethods of oxidizing metals. In cases in which the insulation need notsatisfy high requirements a chemical oxidation may suice; if use is madeof` aluminium or aluminium alloys electrolytic oxidation will generallybe retorted to, it being possible by a proper choice of the material andoxidation conditions to ensureample variation in layer thickness andinsulatingproperties of the oxide layers obtained.

Plates according to the invention formed of Y oxidized metal may be verysimply made by massproduction methods by adopting the following course.A long continuous strip, for example of aluminium, in which the desiredapertures are formed and which may be provided with tags is passedthrough an oxidizing bathA in suchmanner that on discharge from the baththe oxide layer formed has the desired insulating properties even in theapertures, the strip being then severed into individual plates. Thecuttingyedge of a plate made in this manner, which-edge re.- sults fromthe severing operation, has no insulating oxide layer and this isimportant. Thev insulating properties of the oxide layer naturallydepend on the conditions of oxidation, chemical or electrolytic, on bathcompositions, temperature,4 the intensity of current, if used, nature ofthBaIumirIium, duration of the oxidation and so forth. When the startingmaterial used for .an insulating yplate' for the electrodes of awireless valve-isfaluminiumor for exampie an aluminiummagnesium alloy,use may be made of an electrolytic oxidation with '7.6 amp/dm..2 at-ordinary temperatures in an .aqueous solution of 3% by weight ofoxalicacid` taking from 2O to 30 minutes. The layer `thusobtainedy hasathickness of aboutBO/i, a high electric resistance .and a lowloss-factor.

In. order that .the invention may be clearly understeodand readilycarried into effect it -will new .be .described more fully withreference to tlie accompanying drawing, `in which Various forms-of.construction and possibilities of .using aplate according to theinvention are iilustrated.

.Fig f1 is a schematic view oi .a right-angled plane insulating plateaccording to the invention which has formed in it .two apertures for thepassage of electrodes .or other metal parts, I designating theinsulating oxide layer and .2 the unchanged aluminium fundamental metal.

Fig. 2 showsa portion ofthe electrode system ein-an electric dischargetube, 3v designating the anode of the tubeJl, 5 and 6 the suppressorgrid, screen grid and control grid respectively whilst the-cathode isomitted as being not essential to an understanding of the invention inthe present case. The electrodes are maintained at the correctrelativespacing by a. small plate .'l which is. formed as shown in Fig. l. It isapparent trom Fig.. 2 that both an insulating and a screening effect arethus-obtained; thus, .for example, theends of the currentmsupply leads 8ofthe controlgridand the ,cooling .fins Si arranged thereon are. fullgy`screened vfrom the parts of the anode that. arearranged on the othersideof the plate. Relative `screening between the .various parts of gridsand anode that extend on the Youtside of the .plate may beensured by theplate 7 being provided with some few tagsy L0. Suilcient screeninginside the electrode system between anode and. control grid is obviouslyensured by means'oi the screen grid 5.

The spacer of Fig. 3 comprises two parts I4 and i5 the oppositeedges ofwhich have ,formed iny them .registering apertures between which 4 theelectrodes and so forth may be clamped in an insulated manner,`

As set out, 'the plates 'hereinbefore described may be used with greatadvantage in electric discharge tubes where they have to perform variousoperations. It is, however, also possible for these plates to be used atother points in replacement of mica, for example in electric.incandescent lamps to protect the pinch and the stem tube froml Yheatradiated from the glower.

We claim:

l". An kelectric discharge tube comprising an envelope, electrodeswithin the envelope, and means` maintaining a predetermined spacingbetween lsaid electrodes comprising a metallic member within theenvelope having surface portions coated with a supercal insulatinglayer.

2. An electric discharge tube comprising an envelope, electrodes withinthe envelope and means. maintaining. the relativespacing of the said`electrodes. Vcompri-sing a .metallic .plate .having integralsuperi'cially oxidized insulating `surface portions.V

3. An Aelectric discharge. tube comprising .an envelope, electrodes.within-said envelope, and. means maintaining the said electrodes in asub-v stantially fixedspace relationship. comprising. a disk .consistingof a metal including aluminum and having oxidizedinsulating surfaceportions.

d. An electric discharge tube. comprising an envelope, .electrodeswithiny said .envelope having supporting .members `means maintaining.,said, members Yin flxedspace relationship comprising a Vmetallic diskhaving apertures vin which said` members are embraced, said .diskhaving. oxidized insulating surface portions. .including the wallsoirsaid apertures.

5. inthe :manufacture fof an electric. discharge tube, the,methodY ofrfabricating aspacer plate, comprising .the steps` of forming a metalplate to. .a desired shape, .andsurface voxidizing `the plate to ycoatit with van insulating surface layer, thereby tov fabricate a. spacerfor 4insertion in an electricfdischarge tube. v

6. .In..the,man.ufacture oan, electric discharge tube, the; method roffabricating av spacer com.- prising .the steps. of aperturing a strip,of metal, oxidizing said .strip vto. coat it With an insulating surfacelayer, and severing .the .oxidized `strip intof individual plates whichform spacerelements for an .electric discharge tube.

JOHANNES ANTONIUS MARIA VAN LIEMPT. FRITS PRAKKE. HENDRICUS J OI-IANNES`LANDSBERGEN.

JULES HENRI l MARIE, VAN UDEN.

REFERENCES oITEn The following references are of record in the file orthis patent:

,UNITED STATES PATENTS Number Name Date .i2/,2562293 Salzberg Sept.16,1941 2533831701z Cardell Jan. 1K1, 1944

